The long range objectives of this proposal are to examine the microbiologic and immunologic aspects of host defense in sudden infant death syndrome (SIDS). The specific aims of this investigation conducted during the current budget period were 1) to examine the functional aspects of immunologic reactivity in the mucosal surfaces of the respiratory tract in SIDS and in normal healthy living neonates, 2) to determine the prevalence and nature of respiratory viral infections in this community relative to the occurrence of SIDS, and 3) to examine the immunologic and microbiologic status of infants with episodes of apnea.